Back contact solar cell and fabrication method thereof

ABSTRACT

The present invention discloses a back contact solar cell comprising: a first conductive type semiconductor substrate having a front surface and a rear surface of a texturing structure; an oxide layer formed on the front surface of the substrate; at least one first conductive type semiconductor region and second conductive type semiconductor region alternatively formed at predetermined intervals on the rear surface of the substrate; an oxide layer formed on the remaining rear surface of the substrate except for the first conductive type semiconductor region and the second conductive type semiconductor region; and electrodes formed on each of the first conductive type semiconductor region and the second conductive type semiconductor region.

TECHNICAL FIELD

The present invention relates to a fabrication method of a back contactsolar cell, and in particular to a fabrication method of a back contactsolar cell capable of simplifying a fabrication process thereof and alsoreducing fabrication costs thereof by forming a pattern for formation ofa p-type semiconductor region and an n-type semiconductor region on arear surface of the back contact solar cell by a laser method to allow acomplicated process such as photolithography to be omitted.

BACKGROUND ART

Recently, due to problems such as a rapid rise in oil prices, anenvironmental problem of the earth, exhaustion of fossil energy, wastetreatment in nuclear power generation, position selection according toconstruction of a new power plant, etc., interest in renewable energyhas increased and among others, research and development for a solarcell, which is a pollution-free energy source, has actively beenprogressed.

The solar cell, which is a device converting light energy intoelectrical energy using a photovoltaic effect, is divided into a siliconsolar cell, a thin film solar cell, a dye sensitized solar cell, and anorganic polymer solar cell, etc., according to type and configuration ofmaterials. Such a solar cell is independently used as a main powersupply in an electronic watch, a radio, a manless lighthouse, asatellite, a rocket, etc., and is also used as an auxiliary power supplyin connection to a system of a commercial AC power supply. Recently, dueto increase in the necessity for alternative energy, interest in thesolar cell has increased.

A structure of a crystalline silicon solar cell firstly used among thesesolar cells and being also used to some degree in the current solar cellmarket is shown in FIG. 1 . Hereinafter, a fabrication method of aconventional crystalline silicon solar cell will be described withreference to FIG. 1 .

First, a texturing structure for minimizing reflectance of incidentlight is formed on a surface of a p-type silicon substrate 110.Thereafter, an n-type material such as POCl₃ is thermally diffused ontoa whole surface of the substrate 110 to form an n-type semiconductorlayer 120, thereby forming a p-n junction.

Next, an anti-reflection coating 130 for minimizing the reflectance isformed on a surface, which is a light-receiving face in the substrate110, that is, a surface to which solar light is incident. Thereafter,rear electrodes 140 such as an aluminum electrode, etc. are formed on arear surface of the substrate 110 and at the same time, a rear electricfield layer 150 is formed by thermally processing the rear surface ofthe n-type semiconductor layer 120.

Finally, front electrodes 160 penetrating the anti-reflection coating130 to reach to the n-type semiconductor layer 120 are formed tocomplete the crystalline silicon solar cell.

However, such a crystalline silicon solar cell has a disadvantage thatsince there are the front electrodes 160 formed in a metal finger lineform on the surface to which the solar light is incident, that is, thelight-receiving face side, it is impossible to avoid shadowing.

More specifically, the metal finger line is formed in a form protrudedon the light-receiving face so that the shadowing is generated, whereinthe shadowing reduces an area to which the solar light may be incident,thereby having a bad effect on efficiency of the solar cell.

For this reason, the crystalline silicon solar cell has a problem thatit is difficult to generate a high efficiency of 18% or more. In orderto solve the problem, a back contact solar cell has been designed.

FIGS. 2 to 10 show a fabrication process of a conventional back contactsolar cell. Hereinafter, the fabrication process of the conventionalback contact solar cell will schematically be described with referenceto FIGS. 2 to 10.

First, as shown in FIG. 2 , a cut surface of an n-type silicon substrate210 cut in a predetermined size is partially etched and prepared.Thereafter, as shown in FIG. 3 , a texturing structure for minimizingreflectance of incident light is formed on at least one of an uppersurface or a lower surface of the silicon substrate 210 using a basesolution, etc.

Thereafter, as shown in FIG. 4 , a rear surface of the substrate 210 isfinely polished for planarization.

Next, as shown in FIG. 5 , p-type dopant sources 230 and n-type dopantsources 250 are printed on the rear surface of the substrate 210 using ascreen printer, etc. Thereafter, as shown in FIG. 6 , the p-type dopantsources 230 and the n-type dopant sources 250 are diffused to form ann-type region and a p-type region, respectively.

Next, as shown FIGS. 7 and 8 , thermal oxide layers 261 and 263 forsurface passivation and an anti-reflection coating 270 made of siliconnitride SiN_(x), etc., are formed on front and rear surfaces of thesubstrate 210.

Next, as shown in FIG. 9 , the oxide layer 263 formed on the rearsurface of the substrate 210 is partially removed. This process is toform rear electrodes, that is, electrodes electrically contacting thep-type region and the n-type region. In this process, a photolithographyprocess is used in order to remove the oxide layer 263.

More specifically, a photoresist is applied on the oxide layer 263, anda mask having a pattern corresponding to a region of the oxide layer 263to be removed for formation of the rear electrodes is applied thereonand is exposed so that the oxide layer 263 is selectively removed.

After partially removing the oxide layer 263 through this process, therear electrodes 271 and 273 electrically connected to the p-type regionand the n-type region are formed, as shown in FIG. 10 , to complete theback contact solar cell.

The photolithography process is requisite for the fabrication process ofsuch a conventional contact solar cell. That is, the rear electrodeshave been formed in order to solve the problem of efficiencydeterioration due to the shadowing of the conventional crystallinesilicon solar cell; however, it is requisite to partially remove theoxide layer 263 in order to form the rear electrodes and to this end,the photolithography process should be performed.

Such a photolithography process is very complicated as well as causes anincrease in process time and fabrication costs, thereby loweringfabrication efficiency of the back contact solar cell.

Therefore, it is very required to develop technology capable of solvingthe problem of a low efficiency due to the shadowing and at the sametime, fabricating a back contact solar cell only by a simplifiedprocess.

DISCLOSURE Technical Problem

The present invention has been proposed in order to solve the problem inthe prior art as described above. It is an object of the presentinvention to provide a fabrication method of a back contact solar cellcapable of obtaining effects such as rise in efficiency due tominimization of a shadowing effect, which is an original advantage ofthe back contact solar cell, reduction in recombination of electron-holepairs due to the rear surface passivation, etc., and at the same time,accomplishing a simplified fabrication process and a low fabricationcosts, by using a laser method instead of a complicated process such asphotolithography, etc., conventionally used to form a pattern forformation of a p-type semiconductor region and an n-type semiconductorregion comprised in a rear surface of the back contact solar cell.

Technical Solution

In order to accomplish the above object, the present invention providesa fabrication method of a back contact solar cell having a plurality ofdifferent conductive type semiconductor regions on a rear surface of afirst conductive type semiconductor substrate comprising the steps of:forming oxide layers on front and rear surfaces of the substrate; andremoving the oxide layer by irradiating laser light to the oxide layerformed on the rear surface of the substrate at predetermined intervalsto form a pattern of the different conductive type semiconductorregions.

The first conductive type semiconductor substrate may be changedaccording to a conductive type of dopant, and is not necessarily limitedto a specific conductive type, but preferably may be a p-type siliconsubstrate.

In the present invention, the fabrication method of the back contactsolar cell may further comprise the step of alternatively forming afirst conductive type semiconductor region and a second conductive typesemiconductor region by diffusing different conductive type dopants intothe pattern formed at the predetermined intervals. The first conductivetype semiconductor region and the second conductive type semiconductorregion may be an n-type (n+) semiconductor region and a p-type (p+)semiconductor region, respectively.

A method forming the n-type semiconductor region is not specificallylimited, but may be any one n-type dopant doping method selected from agroup consisting of an ion implantation method, a thermal diffusionmethod, and a phosphorous oxychloride (POCl₃) diffusion method. Morespecifically, the n-type semiconductor region may be formed by a methodinserting a p-type substrate into a high-temperature furnace andinjecting an n-type impurity generation gas at a high concentrationthereinto while heating temperature to 800 or 900° C., wherein then-type impurity generation gas may preferably be phosphorous oxychloride(POCl₃).

Also, a method forming the p-type semiconductor region is notspecifically limited, but the p-type semiconductor region may be formedby a screen printing method of a p-type dopant material.

The fabrication method of the back contact solar cell of the presentinvention may further comprise the step of forming metal electrodes oneach of the first conductive type semiconductor region and the secondconductive type semiconductor region after forming the first conductivetype semiconductor region and the second conductive type semiconductorregion.

The metal electrode may be formed by, but not necessarily limited to, ascreen printing method.

In the fabrication method of the back contact solar cell of the presentinvention, a laser source used to irradiate the laser light is notspecifically limited, but preferably may be a green laser source or anNd/YAG laser source.

The fabrication method of the back contact solar cell of the presentinvention may further comprise the step of forming an anti-reflectioncoating on an upper surface of the oxide layer formed on the frontsurface of the substrate.

Also, the front and rear surfaces of the first conductive semiconductorsubstrate may have a texturing structure.

A fabrication method of a back contact solar cell having a plurality ofdifferent conductive type semiconductor regions on a rear surface of ap-type semiconductor substrate according to one embodiment of thepresent invention comprises the steps of: forming oxide layers on frontand rear surfaces of the substrate; forming n-type semiconductor regionsin a pattern in which the oxide layer is removed by irradiating laserlight to the oxide layer formed on the rear surface of the substrate atpredetermined intervals; forming p-type semiconductor regions in apattern in which the oxide layer is removed by irradiating laser lightto the oxide layer between the n-type semiconductor regions atpredetermined intervals from the n-type semiconductor region; andforming metal electrodes on each of the n-type semiconductor region andthe p-type semiconductor region.

A back contact solar cell of the present invention comprises: a firstconductive type semiconductor substrate having a front surface and arear surface of a texturing structure; an oxide layer formed on thefront surface of the substrate; at least one first conductive typesemiconductor region and second conductive type semiconductor regionalternatively formed at predetermined intervals on the rear surface ofthe substrate; an oxide layer formed on the remaining rear surface ofthe substrate except for the first conductive type semiconductor regionand the second conductive type semiconductor region; and electrodesformed on each of the first conductive type semiconductor region and thesecond conductive type semiconductor region.

The first conductive type semiconductor substrate may be a p-typesilicon substrate, and the first conductive type semiconductor regionand the second conductive type semiconductor region may be an n-type(n+) semiconductor region and a p-type (P+) semiconductor region,respectively.

A resultant formed by oxidation will be sufficient as the oxide layer;however, the oxide layer preferably is silicon oxide (SiO₂) formed byrapid thermal oxidation (RTO). Also, the back contact solar cell mayfurther comprise an anti-reflection coating on an upper surface of theoxide layer formed on the front surface of the substrate.

Advantageous Effects

According to the fabrication method of the back contact solar cell ofthe present invention, it is possible to simplify a fabrication process,reduce fabrication time, and reduce fabrication costs by using the lasermethod instead of photolithography in forming the pattern for formationof the p-type semiconductor region and the n-type semiconductor region.

Also, it is possible to obtain effects such as a rise in efficiency dueto minimization of the shadowing effect, which is an original advantageof the back contact solar cell, a reduction in recombination ofelectron-hole pairs due to rear surface passivation, etc.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following description ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view showing a structure of a conventionalcrystalline silicon solar cell;

FIGS. 2 to 10 are schematic views showing a fabrication process of aconventional back contact solar cell; and

FIGS. 11 to 17 are schematic views showing a fabrication process of aback contact solar cell according to one embodiment of the presentinvention.

BEST MODE

Hereinafter, embodiments of the present invention will be described indetail with reference to accompanying drawings.

FIGS. 11 to 17 are schematic views showing a fabrication process of aback contact solar cell according to one embodiment of the presentinvention. Hereinafter, the fabrication process of the back contactsolar cell according to the present invention will be described withreference to FIGS. 11 to 17 .

First, as shown in FIG. 11 , a texturing structure is formed on at leastone of a front surface and a rear surface of a p-type silicon substrate310. The texturing structure may usually be formed in a pyramid shape,etc, and performs a function of reflecting solar light incident to thesolar cell so that maximum light may be absorbed into an inside of thesolar cell, thereby raising efficiency of the solar cell.

The texturing structure may be formed by etching using a known etchingmethod. As an example, the texturing structure may be formed byimmersing the silicon substrate 310 in a basic etching solution such astetramethylammonium hydroxide (TMHA), potassium hydroxide (KOH), orsodium hydroxide (NaOH), etc., to which surfactant such as isopropylalcohol (IPA), isopropyl ethanol (IPE), etc., is added.

After forming the texturing structure, thermal oxide layers 321 and 323for surface passivation are formed on the front and rear surfaces of thesilicon substrate 310. The passivation layers 321 and 323 have a role ofstabilizing and protecting the surface and minimizing surfacerecombination of electron-hole pairs to increase efficiency of the solarcell.

These passivation layers 321 and 323 may be thermal oxide such assilicon oxide (SiO₂), etc., formed by a rapid thermal oxidation (RTO)scheme performed inside a furnace for rapid thermal processing (RTP), asdescribed above. Also, the passivation layers 321 and 323 may be formedby a sputtering method using the silicon oxide (SiO₂) as a targetmaterial.

After forming the passivation layers 321 and 323, a pattern fordiffusing an n-type material is formed on the rear surface of thesilicon substrate 310, as shown in FIG. 12 .

The formation of the pattern is to partially remove the oxidation layer323 already formed on the rear surface of the silicon substrate 310,thereby making it possible to diffuse an n-type material through theremoved portion.

A process forming the pattern by partially removing the oxide layer 323may be performed by irradiating laser light. As a light source of theirradiated laser light, various light sources may be used; by way ofexample, a green laser source with a wavelength of about 532 nm, anNd/YAG laser source with a wavelength of about 1064 nm, etc., may beused.

After partially removing the oxide layer 323, an n-type material 330 isdiffused into portions at which the oxide layer 323 is removed, as shownin FIG. 13 .

As a method diffusing the n-type material 33, a thermal diffusionmethod, etc., may be used. By way of example, a method performing dopingby inserting the p-type silicon substrate 310 into a high-temperaturefurnace and flowing the n-type material (for example, POCl₃) into aninside of the furnace may be used.

After diffusing the n-type material 330, the oxide layer 323 is removedin order to form a p-type semiconductor region in a region except forthe region into which the n-type material is diffused, as shown in FIG.14 . At this time, a certain amount of the oxidation layer 323 is leftin a region close to the region into which the n-type material 330 isdiffused in order to insulate between the region into which the n-typematerial 330 is diffused and the p-type semiconductor region.

At this time, the oxide layer 323 may also be removed by irradiatinggreen laser light with the wavelength of about 532 nm, Nd/YAG laserlight with the wavelength of about 1064 nm, etc.

The oxide layer 323 left in order to isolate the region into which then-type material is diffused and the p-type semiconductor region mayperform a function of a rear passivation layer of the back contact solarcell. That is, the remaining oxide layer 323 protects the rear surfaceof the silicon substrate 310 as well as prevents rear surfacerecombination of electron-hole pairs so as to be able to contribute toimprovement in efficiency of the solar cell.

After removing all oxide layer 323 except for a certain amount of theoxide layer 323 for isolating the region into which the n-type material330 is diffused and the p-type semiconductor region among the oxidelayer 323 formed on the rear surface of the silicon substrate 310, thep-type semiconductor region 340 is formed by printing an aluminum (Al)metal, etc. in a region except for the region into which the n-typematerial is diffused, as shown in FIG. 15 . The printing of the aluminum(Al) metal, etc., for forming the p-type semiconductor region 340 may beperformed by a screen printing method, etc., which is a well-knownprinting method.

In fabrication of the back contact solar cell of the present invention,since the removal of oxide layer 323 required for diffusing the n-typematerial 330 and the removal of the oxide layer 323 required for formingthe p-type semiconductor region 340 are performed by irradiating thelaser light, it is possible to omit a photolithography processrequisitely used to remove the oxide layer on the rear surface of theconventional back contact solar cell. Since the photolithographyprocess, which is a complicated and expensive process, may be omitted,it is possible to simplify the fabrication process of the back contactsolar cell and also reduce fabrication costs.

After forming the p-type semiconductor region 340, an anti-reflectioncoating 370 is formed on an upper surface of the oxide layer 321 formedon the front surface of the p-type silicon substrate 310, as shown inFIG. 16 . The anti-reflection coating 370 may be deposited using adeposition method such as a plasma enhanced chemical vapor deposition(PECVD) method, a sputtering method, or a spin coating method, etc., andbe made of a material such as silicon nitride (SiN_(x)) or titaniumdioxide (TiO₂), etc. This anti-reflection coating 370 may have afunction of minimizing reflectance of the solar cell and at the sametime, perform a function of a passivation layer. Accordingly, defects ofthe back contact solar cell are minimized and recombination ofelectron-hole pairs is further reduced, so that the efficiency of thesolar cell may be improved.

After forming the anti-reflection coating 370, electrodes are printed oneach of the regions into which the n-type material is diffused and thep-type semiconductor region 340 to form rear electrodes 390, therebycompleting the back contact solar cell, as shown in FIG. 17 . As theelectrode 390, a metal with a high conductivity such as silver (Ag),etc., may be used.

Although the present invention has been illustrated with regard tospecific details such as specific components, etc, limited embodiments,and drawings, the specific details such as specific components, etc, thelimited embodiments, and the drawings are only provided in order toassist overall understanding of the present invention. The preventinvention is not limited to the above embodiment, but may be variouslymodified and altered by those skilled in the art.

Therefore, a technical idea of the present invention is not limited tothe above-mentioned embodiment and claims described below andequivalents thereof are within a scope of the technical idea of thepresent invention.

INDUSTRIAL APPLICABILITY

According to the fabrication method of the back contact solar cell ofthe present invention, it is possible to simplify a fabrication process,reduce fabrication time, and reduce fabrication costs by using the lasermethod instead of photolithography in forming the pattern for formationof the p-type semiconductor region and the n-type semiconductor region.

Also, it is possible to obtain effects such as a rise in efficiency dueto minimization of the shadowing effect, which is an original advantageof the back contact solar cell, a reduction in recombination ofelectron-hole pairs due to rear surface passivation, etc.

The invention claimed is:
 1. A fabrication method of a back contactsolar cell having a plurality of different conductive type semiconductorregions on a rear surface of a first conductive type semiconductorsubstrate, the method comprising: forming a pyramid-shaped fronttexturing structure and a pyramid-shaped rear texturing structure atfront and rear surfaces, respectively, of the substrate via etching byimmersing the substrate in an etching solution; forming thermal oxidelayers both on the front and rear surfaces, respectively, of thesubstrate at the pyramid-shaped front and rear texturing structuresusing a rapid thermal oxidation scheme in a rapid thermal processingfurnace or by a sputtering method using silicon oxide as a targetmaterial; forming first patterns by locally removing a thermal oxidelayer formed on the rear surface of the substrate from among the thermaloxide layers by irradiating a laser light to the thermal oxide layerformed on the rear surface at predetermined intervals, and thepyramid-shaped rear texturing structure is not present where the thermaloxide layer is partially removed; forming first conductive typesemiconductor regions on the rear surface of the substrate through thefirst patterns by thermal diffusion in a high-temperature furnace byflowing a first conductive type material into an inside of thehigh-temperature furnace to dope the first conductive type material atthe first patterns; forming, subsequent to the forming the firstconductive type semiconductor regions, second patterns by locallyremoving the thermal oxide layer formed on the rear surface of thesubstrate by irradiating a laser light to the thermal oxide layer formedon the rear surface that remains at the predetermined intervals with thefirst patterns, and the pyramid-shaped rear texturing structure is notpresent where the thermal oxide layer is partially removed, and thepyramid-shaped rear texturing structure remains only between the firstconductive type semiconductor regions and second conductive typesemiconductor regions at the rear surface of the substrate; forming thesecond conductive type semiconductor regions on the rear surface of thesubstrate through the second patterns by a dopant screen printing toprint a second conductive type material to dope the second conductivetype material at the second patterns so that the first conductive typesemiconductor regions and the second conductive type semiconductorregions are respectively formed by different doping methods; and formingfirst electrodes being in direct contact with the first conductive typesemiconductor regions through the first patterns and second electrodesbeing in direct contact with the second conductive type semiconductorregions through the second patterns, wherein a thermal oxide layer atthe front surface acts as a front protection layer, wherein, in theforming of the first conductive type semiconductor regions by thethermal diffusion, the thermal oxide layer at the rear surface acts as amask for protecting portions corresponding to the second conductive typesemiconductor regions at the rear surface, wherein, after the forming ofthe second patterns, the thermal oxide layer at the rear surface remainsbetween the first patterns and the second patterns and acts as a rearprotection layer, wherein the thermal oxide layer remaining on the rearsurface is spaced apart so as not to overlap the first conductivity typeregions and the second conductivity type regions in a verticaldirection, and wherein the first electrodes are formed so as to cover anentire surface of the first conductive type semiconductor regions andextend over an adjacent portion of the thermal oxide layer at the rearsurface, and the second electrodes are formed so as to cover an entiresurface of the second conductive type semiconductor regions and extendover an adjacent portion of the thermal oxide layer at the rear surface.2. The fabrication method of the back contact solar cell according toclaim 1, wherein the first electrodes or the second electrodes areformed by a screen printing method.
 3. The fabrication method of theback contact solar cell according to claim 1, wherein a laser sourceused to irradiate the laser light is a green laser source or an Nd/YAGlaser source.
 4. The fabrication method of the back contact solar cellaccording to claim 1, the method further comprising forming ananti-reflection coating on an upper surface of the thermal oxide layerformed on the font surface of the substrate from among the thermal oxidelayers.
 5. The fabrication method of the back contact solar cellaccording to claim 1, wherein the pyramid-shaped front texturingstructure on the front surface of the substrate is entirely formed onthe front surface of the substrate.
 6. A fabrication method of a backcontact solar cell having a plurality of different dopant typesemiconductor regions on a rear surface of a p-type semiconductorsubstrate, the method comprising: forming a pyramid-shaped fronttexturing structure and a pyramid-shaped rear texturing structure,respectively, of the substrate via etching by immersing the substrate inan etching solution; forming thermal oxide layers on the front and rearsurfaces, respectively, of the substrate at the pyramid-shaped front andrear texturing structures using a rapid thermal oxidation scheme in arapid thermal processing furnace or by a sputtering method using siliconoxide as a target material, forming first patterns by locally removing athermal oxide layer formed on the rear surface of the substrate fromamong the thermal oxide layers by irradiating a laser light to thethermal oxide layer formed on the rear surface at predeterminedintervals; forming n-type semiconductor regions on the rear surface ofthe substrate through the first patterns by thermal diffusion in ahigh-temperature furnace by flowing an n-type conductive material intoan inside of the high-temperature furnace to dope the n-type conductivematerial at the first patterns; forming, subsequent to the forming then-type semiconductor regions, second patterns by locally removing thethermal oxide layer formed on the rear surface of the substrate byirradiating a laser light to the thermal oxide layer formed on the rearsurface that remains at the predetermined intervals with the firstpatterns, wherein p-type semiconductor regions are partially formed atthe rear surface of the substrate to correspond to the second patternsby a dopant screen printing to print a p-type conductive material todope the p-type conductive material at the second patterns so that then-type semiconductor regions and the p-type semiconductor regions arerespectively formed by different doping methods; and forming firstelectrodes being in direct contact with the n-type semiconductor regionsthrough the first patterns and second electrodes being in direct contactwith the p-type semiconductor regions through the second patterns,wherein the rear surface of the substrate has the pyramid-shaped reartexturing structure for reducing reflectance of incident light atintervals between the n-type semiconductor regions and the p-typesemiconductor regions, wherein the pyramid-shaped rear texturingstructure is partially formed at the rear surface of the substrate,wherein the pyramid-shaped rear texturing structure is not formed atportions of the substrate corresponding to where the n-typesemiconductor regions and the p-type semiconductor regions arepositioned, wherein a thermal oxide layer at the front surface acts as afront protection layer, wherein, in the forming of the n-typesemiconductor regions by the thermal diffusion, the thermal oxide layerat the rear surface acts as a mask for protecting portions correspondingto the p-type semiconductor regions at the rear surface, wherein, afterthe forming of the second patterns, the thermal oxide layer at the rearsurface remains between the first patterns and the second patterns andacts as a rear protection layer, wherein the thermal oxide layerremaining on the rear surface is spaced apart so as not to overlap then-type semiconductor regions and the p-type semiconductor regions in avertical direction, and wherein the first electrodes are formed so as tocover an entire surface of the first conductive type semiconductorregions and extend over an adjacent portion of the thermal oxide layerat the rear surface, and the second electrodes are formed so as to coveran entire surface of the second conductive type semiconductor regionsand extend over an adjacent portion of the thermal oxide layer at therear surface.
 7. The fabrication method of the back contact solar cellaccording to claim 1, wherein the pyramid-shaped rear texturingstructure of the rear surface of the substrate is one that remains afterthe forming of the second patterns.
 8. The fabrication method of theback contact solar cell according to claim 6, wherein the rear surfaceof the substrate has the pyramid-shaped rear texturing structure at theintervals between the n-type semiconductor regions and the p-typesemiconductor regions, and wherein the pyramid-shaped rear texturingstructure of the rear surface of the substrate is one that remains afterthe forming of the second patterns.
 9. The fabrication method of theback contact solar cell according to claim 1, wherein a first portion ofthe rear surface of the substrate having the pyramid-shaped reartexturing structure on the rear surface of the substrate is differentfrom a second portion of the rear surface of the substrate that is otherthan the first portion.
 10. The fabrication method of the back contactsolar cell according to claim 1, wherein intervals between the firstconductive type semiconductor regions and the second conductive typesemiconductor regions have portions that are without the pyramid-shapedrear texturing structure of the rear surface of the substrate.
 11. Thefabrication method of the back contact solar cell according to claim 6,wherein the intervals between the n-type semiconductor regions and thep-type semiconductor regions have portions that are without thepyramid-shaped rear texturing structure of the rear surface of thesubstrate.
 12. The fabrication method of the back contact solar cellaccording to claim 1, wherein the entire surface of the first conductivetype semiconductor regions is equal to an exposed surface formed by anopening formed by the first pattern, and the entire surface of thesecond conductive type semiconductor regions is equal to an exposedsurface formed by an opening formed by the second pattern, and whereinthe entire surface of the first conductive type semiconductor regionsand the entire surface of the second conductive type semiconductorregions are parallel to the rear surface.
 13. The fabrication method ofthe back contact solar cell according to claim 6, wherein the entiresurface of the n type semiconductor regions is equal to an exposedsurface formed by an opening formed by the first pattern, and the entiresurface of the p-type semiconductor regions is equal to an exposedsurface formed by an opening formed by the second pattern, and whereinthe entire surface of the n-type semiconductor regions and the entiresurface of the p-type semiconductor regions are parallel to the rearsurface.